The present invention relates to an image sensing apparatus and method and, more particularly, to an image sensing apparatus and method which obtains an image of high resolution by processing images of a document and a scene.
FIG. 20 is a block diagram illustrating a configuration of a conventional high resolution image sensing apparatus. In FIG. 20, reference numeral 1 denotes an optical lens; 2, an iris diaphragm; 3, an optical system driver; 4, a plane parallel plate, which is installed so as to be rotatable, for shifting the light path of an optical image; 5, a controller for controlling the plane parallel plate 4; and 6, a single CCD type color image sensor (simply referred as xe2x80x9ccolor image sensorxe2x80x9d, hereinafter) which is provided with a complementary color mosaic filter (magenta, green, cyan and yellow).
Further, reference numeral 7 denotes a synchronizing signal generator (SSG); 8, a system controller for controlling the entire apparatus; 9, a sample-and-hold (S/H) and automatic gain control (AGC) circuit; 10, an analog-digital (A/D) converter; 11, a first memory for storing complementary color images; 12, -a memory controller for controlling the first memory 11; 13, a color processing circuit for converting the complementary color images to RGB color images; 14, a second memory for storing the RGB color images obtained by performing the color processing on the complementary color images by the color processing circuit 13; 15, a memory controller for controlling the second memory 14; and 16, a timing signal generator (TG).
Next, an operation of the image sensing apparatus having the aforesaid configuration will be briefly explained. Light incoming from outside passes through the optical lens 1, the iris diaphragm 2, then the plane parallel plate 4. The path of the light is shifted by the plane parallel plate 4, and an image is formed on the photosensing surface of the color image sensor 6 and sensed.
FIG. 14 is an explanatory view showing how the path of the incoming light is shifted.
Image signals of the image sensed by the color image sensor 6 are processed with sample-and-hold operation and amplified by the S/H and AGC circuit 9, then analog-digital conversion performed by the A/D converter 10.
Thereafter, the digital image data is stored in the first memory 11. The stored image data is then applied with color processes by the color processing circuit 13, and the resulting R, G and B image data is stored in the second memory 14.
Upon sensing an image by the aforesaid image sensing apparatus, the image formation position of the optical image on the color image sensor 6 is shifted by a predetermined amount (pixel shifting) by tilting the rotatable plane parallel plate 4 by a predetermined angle, a plurality of images are sensed at different image formation positions, then the sensed images are combined, thereby generating an image of high resolution. In a conventional pixel shifting method, the image formation positions of an image are shifted as shown in FIGS. 15A to 18D, for example.
Here, the pixel shifting method shown in FIGS. 15A to 18D is explained. Four complementary color component data is necessary for each pixel in order to obtain an R, G and B image data. To obtain the four complementary color component data, first, an image formed on the color image sensor 6 at the position shown in FIG. 15A is sensed, then the image is shifted from the image formation position shown in FIG. 15A to the left by one pixel to the position shown in FIG. 15B, where another image is sensed.
Next, the image is shifted upward from the position shown in FIG. 15B by one pixel to the position shown in FIG. 15C, and another image is sensed there, then shifted to the right by one pixel to the position shown in FIG. 15D. At this position, another image is sensed. Accordingly, an,image is shifted three times and images are sensed at each image formation position.
Consequently, four complementary color component data of magenta (Mg), green (Gr), cyan (Cy) and yellow (Ye) are obtained for each pixel. In order to obtain an image of better resolution, the image is shifted to the left by half pixel, and with respect to this image formation position (reference position), the aforesaid pixel shifting by one pixel is performed (refer to FIGS. 16A to 16D). This operation is repeated two more times as shifting the reference position upward then to the right by half pixel (FIGS. 17A to 18D). Thus, complementary color images are sensed at positions shifted by a half pixel from each other by performing the aforesaid pixel shifting operation.
However, in the aforesaid conventional pixel shifting method, the pixel shifting by one pixel for obtaining four complementary color component data for each pixel is performed even in a case of sensing a black-and-white image. Accordingly, in the conventional image sensing apparatus, even though a black-and-white image is to be sensed, the numbers of times for shifting an image formation position and for sensing images are the same as those for sensing a color image. As a result, it takes an unnecessarily long time to obtain image data for generating a black-and-white image of high resolution.
The present invention has been made in consideration of the above situation, and has as its object to reduce the numbers of position shiftings for image formation on a color image sensor and for sensing images, performed in order to generate an image of high resolution, when sensing a black-and-white image.
According to the present invention, the foregoing object is attained by providing an image sensing apparatus having a single CCD type color image sensor and shifting means for shifting an image formation position on the single CCD type color image sensor, where the single CCD type color image sensor senses an image of an object formed at each image formation position shifted by the shifting means, the apparatus comprising: determination means for determining whether the object is a color object for which color image sensing operation is suitable or the object is a black-and-white object for which black-and-white image sensing operation is suitable; shifting control means for controlling the shifting means to perform different pixel shifting methods in a case where the object is a color object and in a case where the object is a black-and-white object in accordance with a determination result by the determination means; and luminance component extraction means for extracting luminance signals from color component data of each color of a filter provided on the single CCD type color image sensor when the object is determined to be a black-and-white object by the determination means.
With the above configuration, an image sensed by a single CCD type color image sensor is determined as a color image or a black-and-white image, and when it is determined to be a black-and-white image, only pixel shifting operation by a half pixel for increasing the resolution of an image is performed, and the pixel shifting operation by a pixel for obtaining each color component data for each pixel is not performed. In addition, when the sensed image is a black-and-white image, a luminance component is extracted from each color component data of the complementary colors by a filter provided on the color image sensor, and a black-and-white image is generated by using the extracted luminance signals.
According to the present invention, the foregoing object is also attained by providing an image sensing apparatus having a single CCD type color image sensor and shifting means for shifting an image formation position on the single CCD type color image sensor where the single CCD type color image sensor senses an image of an object formed at each image format ion position shifted by the shifting means, the apparatus comprising: color/black-and-white designation means for designating whether an image to be sensed is a color image or a black-and-white image; shifting control means for controlling the shifting means to perform different pixel shifting methods in a case where a color image is designated by the color/black-and-white designation means and in a case where a black-and-white image is designated by the color/black-and-white designation means; and luminance component extraction means for extracting luminance signals from color component data of each color of a filter provided on the single CCD type color image sensor when a black-and-white image is designated by the determination means.
With the above configuration, an image sensing operation is selected based on whether a color image is to be sensed by the single CCD type color image sensor or a black-and-white image is to be sensed. To sense a black-and-white image, only the pixel shifting operation by half pixel for increasing the resolution of an image is performed, and the pixel shifting operation by a pixel for obtaining each color component data for each pixel is not performed. In addition, when sensing a black-and-white image, a luminance component is extracted from each color component data of the complementary colors by a filter provided on the color image sensor, and a black-and-white image is generated by using the extracted luminance signals.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.